The term "security institution" is intended to refer to penal facilities and mental health facilities where, for the protection of the public, persons under the care of the institution must be confined. Grilles are gratings which cover openings. In this context we are primarily concerned with air grilles, that cover air flow openings in the ventilation system. Air grilles intended for installation in such security institutions must be of reinforced construction in order to prevent the escape of the inmates. An ongoing problem with such air grilles has been the propensity of some inmates to inflict injury upon themselves by suspending themselves from the air grilles. A number of deaths have occurred as a result of such "hangings". The inmates hang themselves from the air grilles by threading a makeshift rope made of braided material through an air passage, up over a structural member of the air grille and back down where it can be tied.